rust-lang/rust — pull request #20045 by alexcrichton (2014-12-19 20:51:57+00:00)
Title: std: Re-enable at_exit()

The new semantics of this function are that the callbacks are run when the *main
thread* exits, not when all threads have exited. This implies that other threads
may still be running when the `at_exit` callbacks are invoked and users need to
be prepared for this situation.

Users in the standard library have been audited in accordance to these new rules
as well.

Closes #20012